1. Field of the Invention
The invention relates to a process for the hygienization of carbonation sludges by a thermal treatment.
2. Description of the Prior Art
In the production of sugar from sugar beet or sugar cane in the sugar industry; the so-called raw juice is initially obtained. This raw juice contains impurities, mainly organic compounds, such as sucrose and protein, as well as phosphoric acid.
This raw juice is purified by adding milk of lime thereto, which binds the impurities. After carbonic acid has been introduced, calcium carbonate and calcium phosphate precipitate together with the other impurities, a fine sludge being formed which is called carbonation sludge.
This carbonation sludge thus represents a primary product from the purification of sugar and it consists in general of 50% of water, 40% of calcium carbonate and 10% of organic constituents. The organic constituents are mainly composed of sucrose and aminoglucose. In addition, the carbonation sludge contains phosphate in a quantity of 0.7% by weight, included in the calcium carbonate figure.
The carbonation sludge is thickened, with the aid of drum filters, to give a mass which can be pumped, and it is finally dumped in large sludge ponds. In these so-called settling ponds, the water slowly seeps into the ground and, during the summer months, it also evaporates. This manner of waste disposal entails considerable environmental problems:
serious odor nuisances arise during fermentation and digestion; PA1 the water seeping into the subsoil can endanger the ground water; and PA1 due to the high oxygen demand during fermentation and digestion of the sludge, the settling ponds require considerable areas. PA1 Domestic refuse: 1,800 kcal/kg PA1 PVC: 4,500 kcal/kg PA1 Polyethylene: 8,000 kcal/kg PA1 Organic shredder wastes: 4,500-6,000 kcal/kg PA1 Waste oil: 8,000-9,000 kcal/kg Acid resins: 4,000 kcal/kg PA1 Bleaching earths: 3,400-5,000 kcal/kg PA1 Old tires: 7,000-8,500 kcal/kg.